The polypeptide antibiotic gramicidin A is the best characterized macromolecule which forms ion-specific transmembrane channels. Evidence from chemical labeling, selective-extraction, and preliminary reconstitution experiments have suggested that the red cell membrane protein Band 3, and possibly also glycophorin A, may play some role in regulating the anion permeability of the human redblood cell. We are incorporating specifically fluorescent labels and 13C nuclei into these macromolecules and we are using spectroscopic techniques to determine the structure and dynamics of these channels in order to elucidate their function in selectively facilitating the diffusion of ions. We are studying how the cytoskeleton of the red blood cell membrane controls the lateral mobility of fluorescently labelled Band 3 and glycophorin A using the fluorescence photobleaching recovery technique. If there is a specific stable complex between Band 3 and glycophorin, then they should have identical lateral mobility parameters. We have already used fluorescence techniques to demonstrate that all of the gramicidin molecules in liposomes are involved in dimer channels; we have used 13C and 19F nuclear magnetic resonance spectroscopy to show that the conformation of the gramicidin A transmembrane channel in lipid vesicles is that of an N-terminal to N-terminal dimer of helices. Fluorescence energy transfer will be used to study the aggregation of fluorescently labeled derivatives of the red cell membrane protein glycophorin A in detergents and in reconstiuted membranes. Similarly, 13C nuclear magnetic resonance will be used to study the conformation of glychophorin after specific 13C enrichment. These studies may provide insight into the structural basis for red cell anion permeability and into cytoskeletal control of membrane protein distribution and mobility.